Process for softening water and dissolving calcium salts with thiotetraphosphates



Patented Jan. 12, 1937 PROCESS FOR 2,067,628 SOFTENING WATER ANDDISSOLVING CALCIUM SALTS WITH THIO- T'ETRAPHOSPHATES Augustus H. Fiske,Warren, and Charles S. Bryan,

Providence, R. I., assignors to Rumford Chemical Works, Rumford, R. I.,a corporation of Rhode Island No Drawing. Application May 15, 1936,

Serial No. 79,916

. 5 Claims.

. Our invention relates particularly to a method for softening water,such, for-instance, as water which is hard by reason of the presence ofcalcium or other salts, and for dissolving these salts in such a manneras todecrease or eliminate the hardness of the water, and particularlyby the use of soluble thiotetraphosphates.

The object of our invention is to provide a more advantageous method forthe softening of water so as to eliminate the hardness thereof, bydissolving .the said salts with the aid of soluble thiotetraphosphates,that is to say, the thiotetraphosphates of the alkali metals. Thesethiotetraphosphates have been recently discovered by us and are thesubject of U. S. Patents Nos.

2,025,503 and 2,033,913, as, for example, sodium monothiotetraphosphate, NasP40'12S, or sodium trlthiotetraphosphate,NaeP401uSa, or the corresponding potassium Orammonium salts.v

The water softening maybe carried out according to our method by usingthe true alkali thiotetraphosphates, made in' accordance with theprocedures described in the above patents.

' We particularly recommend the sodium thiotetraphosphates for ourpurposes as being most cheaply made and giving excellent results, thoughany other soluble thiotetraphosphate or thiotetraphosphates may be usedfor our purposes and in our process.

While our invention is capable of being carried out in many difierentways, for' the purpose of illustration we have described hereinafteronly certain embodiments of our invention.

The water softener made in accordance with our invention may be appliedin such a manner as to soften the water containing soluble calcium saltswith or without the presence'of other soluble salts, as, for instance,magnesium salts, for the following uses:

As a water softener lfy keeping the alkali earth basesin a solublecondition.

In laundries to save soap by combining with the alkali earth bases inthe washing water.

In deliming leather as in the tanning industry. In dissolving the limecompounds which may occur in soiled textiles. To prevent deposits ofalkali earth salts forming in hot water systems.

- in automobile To prevent the formation of alkali earth'precipitates onthe outside of cans from the cooling water of the canning industry.

To prevent streaky dyeing in textiles by keeping any alkali earthcompounds in a condition of solubility.

Preventing the formation of soap spots on the cloth in dyeing.

To clean: cement or brick walls from lime deposits.

As a softener for water in washing living animals or in baths for humanbeings.-

For cleaning or washing dishes.

For softeningwater in which anything may be washed and thus saving soap.

Washing rayon, for instance.

'Scouring wool.

Kier boiling in bleacheries.

Boiling ofi silk.

Causing increased penetration of dye in tex-- tiles by cleaning ofitraces of alkali earth compounds.

As so applied it is found that the water softening by adding an alkalimetal thiotetraphosphate is much more effective than previous methods ofwater softening. For example, to soften the water used in laundries forthe washing of fabrics, or in preventing the deposit of alkali earthcompounds in steam boilers and other feed lines, with water containingsoluble lime salts with or without the presence of magnesium salts,etc., we add to 1000 gallons of water containing, for instance, 48 partsby weight of calcium per million of water, in the form of soluble salts,usually sulphates, bicarbonates or chlorides, 3 pounds of a sodiumthiotetraphosphate or 3.6 pounds of a potassium thiotetraphosphate asmade in accordance with either of the above mentioned patents alreadyreferred to. As a result of this treatment the relatively largeconcentration of free calcium ions in the water is very greatly reducedor entirely eliminated by combining them into soluble only slightlyionized compounds or radicals due to the presence of thethiotetraphosphate. It will be found that in the softening of the waterfor steam boilers and feed lines the calcium and other similar compoundsare prevented from being deposited to form a scale in the steam boilersand feed lines, notwithstanding the heating and concentration that takesplace. Similarly, the water may be softened in substantially the sameway in connection with any of the other water softening operations, andparticularly in the other industries listed above.

We have found that water may be softened in this way, in accordance withour process, much more efiectively inasmuch as less of the alkali metalthiotetraphosphate is required to completely soften the water than willbe required of other materials previously used for such purposes. Thiscanbe readily demonstrated by a simple test of the water softeningproperties of these thiotetraphosphates. amount of the water softeningsubstance required to be added to keep the calcium in solution.

While we have mentioned above thiotetraphosphates made only by the twodifferent procedures in U. S. Patents Nos. 2,025,503 and 2,033,913, wedo not wish to confine ourselves-to the products of these two processes.It will be understood that there can be other processes for makingsoluble thiotetraphosphates and it is readily seen that there are manythiotetraphosphates wherein the oxygen atoms of a tetraphosphate may bereplaced by a sulphur atom. -For instance, the sodiummonothiotetraphosphate, Na6P4Oi-2S may be prepared according to U. S.Patent No. 2,025,503, but there are many other possible thic--tetraphosphates, for example:

NasPsOuSz NasP iOssa NaaBrOmSa N MP4O4S9 NauPaOeSa. NasRzOaSw NaePgOaSsNaeBzOzSn NasPaOvSc N36P4OS12 NaeP40eS'I NaSPASIS so given in the aboveexamples of the difierent thic- This is demonstrated by thetetraphosphates where one or more of the sulphur atoms replaces theoxygen atoms in its formula.

The property of a thiotetraphosphate to give it water softening qualityis probably, in our-opinion, its ready solubility in water and allsoluble thiotetraphosphates will be found to have the power of softeningwater.

While we have described our invention above in detail we wish it to beunderstood that many changes may be made therein without departing fromthe spirit of the same.

We claim:

1. A process which comprises adding to hard water a water-soluble saltof a thiotetraphosphoric acid so as to combine with an alkali earthmetal to prevent the deposition of an alkali earth metal compoundtherein.

2. A process which comprises adding to hard water a water-soluble saltof a thiotetraphosphoric acid so as to combine with calcium to preventthe deposition of a calcium compound therein.v

3. A process which comprises adding to hard water an alkali metal saltof a thiotetraphosphoric acid so as to combine with an alkali earthmetal to prevent the deposition of an alkali earth metalcompoundtherein.

4. A process which comprlsesadding to hard water a water-soluble salt ofmonothiotetraphosphoric acid so as to combine with an alkali earth metalto prevent the deposition of an alkali earth metal compound therein.

5. A process which comprises adding to hard water a water-soluble saltof trithiotetraphosphoric acid so as to combine with an alkali earthmetalto prevent the deposition of an alkali earth metal compoundtherein.

AUGUSTUS H. FISKE. CHARLES S. BRYAN.

